Telegraph system and printing apparatus



Oct. 17, 1944. 1." M. POTTS TELEGRAPH SYSTEM AND PRINTING APPARATUS 4 Sheets-Sheet 1 Filed .Nov. 12, 1942 FIG. 1 I

ua H19 INVENTOR. LOUIS M. POTTS- ATT RNEY.

Oct. 17, 1944. M, -rs 2,360,580

TELEGRAPH SYSTEM AND PRINTING APPARATUS Y Filed Nov. 12, 1942 4 Sheets-Sheet 5 FIG. 6

STOP TAR l 2 3 4 5 6 7 8 9 IO ll l2 l3 l4 FUNDAMENTAL O WAVE CHARACTER GHARAGTER A v m B v V CHARACTER A U- LETTER q SPACE 1 INQENTOR. LOUIS MPOTTS I BY J2 7 AT ARNEY;

Patented pct. 17, 1944 TELEGRAPH SYSTEM PRINTING APPARATUS Louis M. Potts, Evanston,

Ill., assignor to Teletype Corporation, Chicago, 111., a corporation of Delaware Application November l2, 1942, Serial No. 465,333

19 Claims.

The present invention relates to printing telegraph apparatus and more particularly to apparatus which utilizes alternating current for operating power for phasing between transmitting and receiving station machines, fundamental signal carrier.

The principal object of the invention is to provide an alternating current powered and sync'hronized printing system which is responsive to modulations Or modifications of a fundamental alternating current wave for effecting signal transmission.

Another object of the produce character be operated on a small amount of power such as that transmissible over an ordinary telephone loop circuit and which is controlled by characteristically modifying the power current.

A still further object of the invention is'to provide a. telegraph system utilizing apparatus which may be manufactured and maintained at low cost and which may be operated at moderate speeds of signal transmission while requiring a minimum of local equipment for maintaining synchronism between station apparatuses.

In its basic conception, the system and apparatus of the invention contemplate the use of an alternating current carrier wave preferably having a fundamental frequency of 60 cycles such as is customarily available from commercial sources and having a regulated amplitude sufficient for operating synchronously responsive motors of the rotary or vibrating armature varieties. A'certain'number of current reversals which are conpresent invention is to tinuously impelling the vibrating motor armature effect the step-by-step operation of a rotary moving element throughout a cycle and this number accordingly constitutes a signal of undulations unit during which a variable number of componential character printing operations may be performed. Upon the fundamental wave there is superimposed at variable positions of a signal span or unit either full or half wave amplitude modifications which effect responses at a receiving station apparatus causing printing character images to be composed by assembling together different combinations of a limited number of character fragments.

In the utilization of this'form of signaling, it is proposed that station equipment be provided with apparatus for automatically arresting the print-- mg andtransmitting mechanism in a normal or zero position. From thisposition'and with the and also as .a

printing apparatus which may transmitting and receiving respective motor elements continuing in vibration or rotation at the regulated frequency, the release or start impulse having the form of a modified full or half wave, as preferred, initiates into rotation a receiving shaft at the printing station which thereupon is adapted to describe a cycle of rotation corresponding to a predetermined number of component alternating current wave impulses. During this cycle of rotation one or more wave modifications or modulations are effected upon the fundamental frequency which cause to be operated at a printer station, a print hammer which is responsive marginally to the This stronger cycle causes composition superimposed or modified waves. current at selected periods of the character printing to be effected by a of printing elements or components.

'Within the concept of the present invention, each printing cycle consists of a fixed number of alternating current component waves or wave intervals commensurate with the number of character signals which are used in the composition of the alphabet, or if desired, the number of components may be equal to the number of characters in the alphabet in which case each printing symbol may in fact constitute a complete character. Preferably, however, it is proposed herewith to utilize a character printing type wheel that is made 'up of character fragments. These fragments or component elements may be composed into various combinations so as to form pic- 'torially alphabetical and numerical character representations after the manner of popular convention. It will be understood, of course, that the degree of artistry or perfection of characters will depend upon the number of component elements available within the concept of the system and that for more efficient signal transmission a fewernumber of component elements may suffice to obtain comprehensive characterization of the alphabet or numerals.

For a more comprehensive understanding of the present invention, reference may be had to the accompanying drawings and to the following detailed specification in which-like reference characters designatethroughout and in which,

Fig. 1 is a'perspective view with parts broken away of a vibrating motor telegraph printing apparatus having incorporated therein certain features of the present invention;

Fig. 2 is an exploded detail perspective view 01' structural mechanism of the embodiment featured in Fig. 1;

corresponding parts Fig. 3 is a development of the type wheel periphery featuring the alphabetical and numerical character fragments from which there may be composed alphabetical as well as numerical character representations;

Fig. 4 is a plan ,view of the apparatus featured in Fig.1 having certain portions broken away to reveal the internal construction;

Fig. 5 is a side elevation of the apparatus featured in Fig. 1 having portions of the supporting structure broken away;

Fig. 6 is a curve chart illustrating several typical signal codes as well as wavesof a signal cycle with amplified or modified full wave signal patterns;

Fig. '7 is a diagrammatic circuit illustration of a central station equipment and representations of outlying stations equipment utilizing the principles of the present invention;

Fig. 8 is a diagrammatic circuit illustration of arudimentary application of the present invention for use in nonswitching or one-way installation;

Figs. 9, 10,-and 11 are transverse sectional detail views taken approximately on line 9-9 of Fig. 4 featuring in somewhat enlarged scale the particulars of the spur lever and ratchet wheel apparatus in various positions of operation.

Fig. 12 is a circuit diagram of an adaptation utilizing principles of the present invention;

Fig. 13 is a circuit diagram featuring a rud mentary application of principles of the present invention featuring a nonswitching installation;

and

Fig. 14 is a curve nal examples of prevailing line conditions identiilaed with the systems featured in Figs. 7, l2, and

Referring now particularly to the accompanying drawings there will be described first the structural features and operation of the printing unit illustrated in Figs. 1, 2, 4, and 5. The reference character flgdesignates a supporting base which may itself be mounted upon cushioned legs and upon the upper surface of which there is secured a principal supporting wall 43 that extends in a vertical planetransversely of the length of base 82. Wall 13 is profiled so as to afford a clearance at 44, Fig. 1, for the print hammer controlling line magnet generally designated '85, and as at 46, Fig. 5, to permit the extension iglgerethrough of the type wheel carrying shaft The prime mover which supplies rotary power for the operation of this device consists of a vibrating power shaft 48 journaled within a supporting casting 49, Fig. 4, and carrying at one of its ends in transverse relationship to the shaft 88 the two motor windings 5| and 52, and at its other end a crank pin disc 53 which is mounted concentrically by means of a securement bolt 54 and rigidly held against an anchor plate 55 by means of the securement screw '50 which passes through the arcuate slot 50 of disc 53 and is threaded into the plate 55.

Alternating current from a power source is conducted to the afore-mentioned windings 5| and 52 after a manner already described and disclosed in connection with the apparatus featured in copending application Serial No. 440,653 filed chart illustrating several sig-' and hence simultaneously attractive to the pole pieces 58 and 59. As the shaft rotates in response to either one of its opposite conditions of magnetization, as, for example, when the pole 55 becomes attracted to the'piece 58 and pole 51 to the piece 59, shaft 48 will rotate clockwise as viewed in Fig. l and in so doing the end or anchor plate 55 having secured thereto one terminal of a torque spring 6!, Fig. 4, causes the latters convolutions to become distended.

The coil spring GI thus functions as a tuned reed and the number of its coils which are free, that is, which lie between the point of securement of its first coil in the end or anchor plate 55 and that of an intermediate securement lu 62 may be varied to correspond in natural vibration with the frequency of the current variations and in this way one may regulate the normal periodicity of the spring vibration so that it will accord with the alternating current frequency.

A horseshoe magnet 53 having permanent magnetic characteristics determinesthe olar magnetic nature of the pole pieces 58 and 59. As a result of the oscillatory movement initiated with the vibrating armature of shaft 48 a corresponding motion is imparted to the crank pin disc 53 in the face of which is secured a crank pin ii that extends into a slot 12 of a freely mounted pallet arm 13, Fig. 2.

The operation of the vibrating motor is as follows: When starting, alternating current is applied to the device which biases the armature in one direction and places a small torsion on the spring 5i. As the current is reversed, this torsion is removed and the force built up in the spring 5! together with the force resulting from the current in the reverse direction cause the armatur to be rotated in the opposite direction but to a greater degree since the energy which had been stored in spring 6| now is contributed to the magnetic force of the armature. Because this movement in the opposite direction is somewhat greater than the preceding motion, the energy stored in the spring -6| as a result of this movement is correspondingly greater and contributes to that extent more forc when shaft 48, in response to a new reversal of the current, resumes the original direction of movement. The accumulation of energy and, accordingly, the increase in the amplitude of motion continues in this manner until a condition obtains when the energy lost in each swing of the armature and shaft 48 precisely equals the energy added where- I upon a constant amplitude obtains.

While a certain amount of current is con- .sumed in attaining or in regaining this maximum amplitude of vibration after a load has been April 2'7, 1942. As there explained, the windings 5| and 52 are serially connected and wound in a direction so that the opposite pole faces 56 and 51 become. alternately and oppositely magnetized placed and removed, it is notably an energy loss of smaller degree than that amount which would be otherwise required in the performance of the printing operation if no advantage was had of Y the practice of storing energy from idle oscillation.

While the oscillations imparted to shaft 48 may vary in amount of motion, it is to be noted that the speed of rotation imparted to the type wheel carrying shaft 41 is thereby not affected. This is assured for two reasons, one being that the time of a complete oscillatory cycle does not vary regardless of the amplitude or angle of oscillation, and the other reason being that the crank pin II is designed to impart the same degree of movement to arm 13 regardless of its throw or angl of oscillation.

one or the other of the two arcuate surface 14 or 15 depending upon which way it happens to be moving. On its return movement from either direction of travel, pin 1| rides along said surfaces 14 or 15 until it re-enters the slot 12 whereupon it cause arm 13 to reverse its angle of oscillation, repeating the performance in the opposite direction. Accordingly, overtravel on the part of pin 1| beyond a minimum angle of oscillation or amplitude has no effect on the performance of shaft 41 but instead there is assured a constant rotation to shaft 41 by reason of the step-by-step feed mechanism now to be described.

From Figs. 2, 4, and 9 to 11, it will be clear that arm 13 as well "as its companion ratchet wheel 11 with which it is integrally associated are together freely rotatable on a bushing or sleeve 18 whichis integral with a detent disc 18.

The'teeth of ratchet wheel 11 are engageable by the spur 8| of a pawl lever 82 pivoted at 83. As best revealed in Figs. 9 to 11, pivot 83 is carried by a trip plate 84 that forms part of a revoluble assembly, including the aforementioned detent disc 18.

In this assembly which is carried upon the threaded portion adjacent to the afore-mentioned sleeve 18 is a driving pinion 86, on one side of disc 19. The afore-mentioned plate 84 is held against the shoulder of sleeve 18 by a nut 81 and following it is a type wheel 88 whose periphery comprise a number of flat type carrying faces corresponding to the development indicated in Fig. 3, a lock washer 89 and a retaining nut 8|. When the spur. 8|, which is carried by pawl 82 and which is rotated in a counterclockwise direction above pivot 83 by the influence of a mild tension spring (not shown), engages the teeth of ratchet wheel 11 as the latter member is oscillated to and fro, a step-by-step rotation is imparted to this assembly from the point at which pawl lever 82 is released until the same point at the end of the cycle of rotation when it is again engaged by an arrestment lever. The number of teeth on ratchet wheel 11 is the same as the num- 1 her of. typefaces on type wheel 88 and also the same as the number of detent notche in disc 18.

Thus, whileratchet wheel 11 remains in the same relative position, as indicated by the surface mark V, Figs. 9 to 11, the type wheel sleeve assemblycarrying the pivot 83 of spur lever 82 is advanced in step-by-step manner in a clockwise direction as the spur 8| is pushed from one tooth to another about gear 11.

The rotatable assembly on sleeve 18 comprising the elements afore-recited is supported upon a stud shaft 82 and when pawl lever 82 is held in its clockwise extremepcsition as designated in Fig. 9 by reason of the engagement of its tail portion 83 by the disc extremity 94 of a pivoted lever arm 85, no rotation of the assembly is obtained. However, as soon as the disc lever 85 is withdrawn (counterclockwise) which operation is effected by a tripping of its associated lever arm 86, as will later be explained, the tail 83 of pawl 82 is per mitted under the influence of the latter members spring 88 to move in a counterclockwise direction about pivot 83 until thespur 8| enters into the field traversed by the oscillating teeth of ratchet wheel 11. Each angle of advancement, that is when one of the teeth of ratchet wheel 11 engages the spur 8| and sends it one tooth distance in a clockwise direction, Figs. 9 to 11, about shaft 82,

is retained and the return movement is prevented Lever arm 95 which is pivoted on a screw 88 together with its associated lever arm 88 is urged by spring I88 in a clockwise direction about its pivot until its opposite extremity (shown in dotted outline in Fig. 9) engages a sidewardly extending lug |8I integral with lever arm 86. This spring effects the unified action On the part of levers 85 and 86 subject to the yield afforded by said spring I88. Levers 85 and86 may, therefore, be

considered to act as a unit and moreover lever 86 is provided with a sidewardly extending lug I82 which is engaged by a downwardly urging coil spring I83 whichimparts to the lever assembly 85-86 a counterclockwise torque about pivot screw 88 as a center.

The extremity of lever 86 is provided with an upwardly jutting lug I84 which is engage'able by a downwardly extending projection I85integral with the rotatable trip plate 84 of the assembly, Fig. 2. Also, the lowermost extremity of lever 86 is shouldered as at I86 and thereat is engaged by a, hook I81 that terminates one arm of a trip lever I88 pivoted at I88. Lever I88 is spring urged in a counterclockwise direction and its other arm is provided with a sidewardly extending shelf III that is, in turn, engaged by an adjustable trip screw 2 carried in a ledge of the downwardly extendin branch II3 of an armature II4. v

Armature H4 is supported by an anchor plate II5 through the medium of a flexible tongue II6 connecting the two. This armature which corresponds to the representation designated 68 in Fig. 8 carries at its extremity a print hammer or anvil 'I I1, Fig. 5, which is adapted to strike against the type wheel faces II8 to I33, Fig. 3. Beneath the plate H5 is located 'a permanent magnet I34 and s=nce this element is mounted between the plate H5 and another, plate of electromagnetically permeable material I35 connecting it to the core I36 of an electromagnet 65, a primary mag neitc field is thereby set up affecting armature II 4 preferably so as to bias it downwardly as viewed in Fig. 1. For a theoretical explanation of the operation of this portion of the apparatus,

reference will now be had to 8 in which symbolic representation of a transmission system are indicated in conjunction with a, simplified communication circuit.

The particular system of telegraph transmission now urrder discussion involves specifically the use of a tuned vibrating-armature type of .motor which is adaptable for use with alternating current, though any other class of synchro-g nously driven motor may with but slight changes for adaptation purposes, .also be used. One of the special functions of printer control now to be described is that of print hammer operation, a performance which, in the instant system, may

occur one or more times during each cycle of rotation of the element which carries the type ,wheel. In Fig. 8, the print hammer has been desig-' nated 64 and indicated as an integral element of the biased armature of polar magnet 65 situated at' a receiving station designated generally 61. At a transmitting station, alternating current is obtained from a frequency regulated source. obtained as through the use of a fixed voltage transformer 66 whose secondary winding is grounded at one terminal and connected to line Also at this source, signaling power is 68 at its other terminal after passing through a resistance ID. The latter element limits the current flow over line 68 to an amount which is marginally insuflicient to operate the biased print hammer control magnet 85 because of a bias (described later) influence but is sufficient to actuate the vibrating armature at the receiving station in series with the magnet 65. When the marginal control resistance is shunted out, as by the closure of contact pair '69 of the transmitter keyboard apparatus, then an increased current flow is passed which does overcome the magnetic bias of armature 64, and as a result the latter member will be attracted during strong current pulsations and effect composition printing accordingly.

The print hammer G4 and its integrally associated armature is normally held away from the type wheel and against the influence of a biasing spring and while in this position the normal and relatively'weak alternating current pulsations, prevailing when no character printing signals are superimposed upon the primary wave, are insufiicient to effect the movement of the armature. However, when an amplified signal impulse is received over the line as upon the closure of the contact pair 69 at the transmitting station, armature 6-3 is impelled by the increased current which overcomes its bias and causes it to strike the type wheel during either the plus or minus half of a full alternating current wave, according to the manner in which the magnet winding is designed.

For some purposes it may be preferable to design polar magnet 65 so that the first half wave (plus or minus) of a complete alternating current wave will actuate this armature into performance affording the second half wave interval as time in which to restore the armature fully to its unoperated position. In this way, there may be avoided a condition whereby the initial portion of a signal contributes arr-additional bias force in a direction toward the unoperated position which then must be overcome as an additive force to the normal magnetic bias during the second half wave of a cycle. Tests have proved, that satisfactory supervision of a biased armature print hammer may be had under either conditions o polarity print magnet control.

The present system utilizes a fundamental-alternating current frequency wave represented in Fig. 6 by the reference character 19 and designated by the legend Fundamental Wave. This recurring undulation may be transmitted uninterruptedly to a receiving printer and its effects upon a synchronous wound motor or upon 9. vibrating armature type of motor as is specifically illustrated in the accompanying drawings, is to maintain in motion the stations apparatus with the regularity of the current stabilization factor. The manner of signaling in accordance with the herein proposed system consists in a practice of superimposing a wave amplitude modification or modulation as designated for example by the undulations in the curves A, B, and I, whereat a unit cycle of' operation is designated by a total of sixteen intervallic divisions. These divisions are comprised of fourteen signaling intervals (each interval of which is made up of a full alternating current wave; that is, two half waves of opposite polar characteristics) and two additional signal intervals designated in Fig. 6 by the legends Stop and Start. While the transmission cycle is made up .of sixteen intervals as portrayed by the curves in Fig. 6, the receiver cycle is made up of but fifteen intervals or components as designated by the faces II8 to I42 of the type wheel development, Fig. 3. Fourteen of these components correspond as do the transmission components, to the fourteen printing fragments II8 to I33, while the fifteenth interval corresponds to the start interval of the transmission cycle. Where the receiver cycle is not provided. with a sixteenth interval to correspond with that of the transmission cycle, the receiving printer will rest and thereafter be initiated into a new cycle upon the receipt of the start interval. Thus, during continuous signal transmission the printer shaft will be momentarily brought to rest after each cycle during an intervallic instant which corresponds in duration to one full wave length.

As may be noted, each one of the chartedsignals consists of a full wave modulation during its start interval. Thereafter the occurrence of amplitude modulations varies in accordance with the characteristics of the particular signal code or composition of character fragments. The signal composition of the instant system consists in a number of wave modulations occurring during the respective component interval of which there may be one or more within a band of intervals termed a cycle, which intervals coincide with fragmentary symbols that may be composed to make character designations.v

Referring now to the illustration, Fig. 3, there is indicated an exemplary arrangement of character composition fragment or character elements,

' fourteen in number. The letter A of the alphabet will, in accordance with the illustration of Fig. 1, consist of an amplitude modulation in the first, fourth, sixth, eleventh, and fourteenth intervals which accordingly will be composed of the character fragments illustrated in the developed type wheel, Fig. 3, of the faces designated thereat II8,

I22, I24, I29, and I33. A composite alphabetical character made up of these fragments of printing elements in'the designated order will produce a character that may be readily identified as the alphabetical representation A and after the same manner-alphabetical characters B, C, etc. may be composed as may also the numerical integers l, 2, 3, etc. from the representative arrangement of fragments as designated in Fig. 3. Where a different style or artistic composition of intelligence characters is desired any other pattern differing from the one shown may be produced with perhaps a different number or a more commodious supply of character elements. For the purpose of obtaining a simplified and yet readily discernible alphabet and Arabic numeral series, fourteen character fragments as shown in Fig. 3 have proved ample for practical com-prehensions.

Referring now again to the illustration in Fig. 5, the printing armature II4 vibrates between the poles I31 and I38 of the magnet core I35, Normally, that is, when the operating current wave is received through the winding 65, armature IN remains dormant preferably resting against the bottom pole I38 and.does not then respond by vibrating between its two limit screws I39 and I M; This is the condition which prevails when I no signals are induced upon line 68.

In response to the amplified wave impulse, armature II4 moves from its rest position as indicated in Fig. 5- to its opposite position whereat its extremity abuts limit screw I39. This operas viewed in Fig. 1.

anvil III. The exception prevails at the particular instant that the blank type face I42 is disposed in printing position and this space is called blank because it is provided with no print markingimpressions as are the otherfaces II8 to I33. As a result of the upward movement of portion '3 of armature II4, screw II2 engages the-shelf III of bell crank lever I08 rocking the latter member clockwise about its pivot I09 and releases its hook I01 from the shoulder I06.- This frees lever arm 96 to the influence of its spring I03 and as a result lever 99 as well as its companion lever arm 95 rock in a counterclockwise direction about 99 as a center. v

In consequence of the movement of lever arm 95, its disc extremity94 is withdrawn from engagement withthe tall 93 of pallet lever'82, permitting the latter spur BI to move into position so as to be engaged by the teeth of ratchet wheel I'I.- Thereafter the oscillations of shaft 48 will no longer be idle but instead have the effect of imparting motion to the type wheel carrying assembly, Fig. 2, by reason of the reciprocal action of crank arm 13 and of ratchet wheel 17.

For the duration of one revolution, each succeeding oscillation of shaft 48 will be translated tocrank pin 'II, arm I3, and ratchet wheel I1 as a single-step movement in a counterclockwise (Fig. 2'; direction. of the type wheel carrying assembly. Each such single-step advancement of said assembly is held 'by the spring-urged detent 91 which engages the notches of detent disc 19. Also, it is to be noted that as the assembly rotates in a counterclockwise direction, plate 84 the step-by-step movement neath the type wheel 8 ably supported upon the base 5 I45 is a pressure roller I49 carried upon an arm I5I which is pivoted at I52 and urged in a counterclockwise direction by a pressure spring I53. The tapev after being pulled up to the point of contactual engagement between fluted roller I45 and pressure roller I49 'is pushed thereafter bejust above the anvil II'I exiting through another uide I54.

The printing tape is supplied from a roll I55, Fig. 1, carried upon a shaft I56 between the two vertical guide strips I 51 and I58 that are suit- 42.0f the machines. The tape I45 as it emerges from the periphery of the roll I55 passes through a slotted opening I59 in the supporting wall 43 and thereafter doubles around the edge of theforty-five degree guide plate I6I changing its direction at right angles thereat' and entering the first guide member I48.

- On the accompanying illustrations no specific ink depositing medium has been shown in, order to avoid obscuring the .views. Several methods of ink supply might be used in conjunction with printer type wheels of the class, employed such as an ink reservoir roller contacting an ink distribution roller which in turn contacts wheel 88, or an ink ribbon may be fed'between the being a part of the assembly also describes a cycle of revolution carrying with it engagementtooth I05.

During the cycle of rotation of the type wheel assembly, one or more additional amplified waves or strong impulses will be received causing armature I I4 to vibrate between its limit screws I39 and MI but during the other positions of the cycle, anvil I I! will strike against one or more of the faces II8 to I33. Also during the cycle of rotation, spur lever 82 will be carried around together with its pivot 83 of plate 84 describing a revolution as it does So in a counterclockwise direction until a point is reached near the end of its cycle when its tail or rearmost extremity 93 comes into engagement with the disc 94 which will meanwhile have been replaced to its original position as will now be explained.

Near the end of the cycle of revolution, projection I05 of plate 84 encounters the upstanding extremity I04 of lever arm 96 camming the latter member in a clockwise direction about its pivot 99 until hook I01 re-engages the shoulder I06. This point of engagement occurs after the fourteenth cyclic interval since lever I08 must not again be released until after it has reached the. stopping point in contemplation of a new signal.

The driving pinion 86 which is integrally formed Y with a detent' disc I9 meshes with a drive wheel I43 of a tape feed shaft I44. While the assembly, Fig. 2, is making one cycle of revolutions in a counterclockwise direction, wheel I43 and its integrally associated shaft I44 will describe a few. degrees of rotation in a clockwise direction,

At its foremostextremity, shaft I44 carries a fluted portion I for affording a tractional engagement with the undersurface of thetape I46 which is threaded through the guide member I41 and I44. Cooperating with the fluted extremity anvil I I 'I and the type wheel 88. Ideal results have been obtained by utilizing a double paper strip, on one web of which .there is carried a carbon deposit that is transferred through impact upon the surface of the other strip.

For a general understanding of the practical application of the present invention in a systern designed especially for signal transmission of alternating current fundamental wave signals having character selecting modulations or wave modifications, reference will now be had to the specific illustration in Fig.7 showing a typical circuit arrangement having embodied therein a central oflice exchange system. In this illustration, reference character II denotes in dotted outline a central ofllce exchange system.- provided with-the commercial alternating cur- A rent supplylines I2 and I3, a power transformer comprised of the windings I4 and I5, and a pair of balanced induction control transformers I6 and I I forming part of a cord circuit in the manual exchange system or part of a. link circuit in an automatic exchange system. Characters I8 and I9 indicate two illustrative outlying or subscribers" stations represented by dotted rectangles of which there may be any number similarly communicating with the central station equipment.

At each outlying station I8 or I9 there may be provided a keyboard "transmitter apparatus as:

well as a receiving printer, the latter for recording both outgoing and incoming communication signals. At said stations I8 or I9, the key- I board transmitting equipment is represented by the motor armatures 23 and 23a which are indicated as being in series'circuit connection with a printer motorarmature 24 and 24a from a center tap of local primary transformer windings 25 and 250 whose secondary windings 29 and 25a are in circuit with a printer operating magnet 21 and 21a.

The. keyboard apparatus at each of said stations is adapted to supervise a pair of transmitting contacts 29 and 39a which lie in one of the lines 29 or 3| which linemay form part of a pair of lines connecting each outlying station 8 and the printing regionwith a central ofllce ii, the other lines of said pairs being designated 32 and 33, respectively.

Outlying station I8 connected over its line 29 to one terminal of a winding 34 of the central station transformer generally designated I'I while its other line 32 is connected with one terminal of the winding 35 of another central station transformer generally designated I5, the adjacent terminals of said windings 34 and 35 being connected together and joined thereat by a line 36 from one of the terminals of the power winding I which is carried over line 36 to the transformer is connected in a similar manner with station I9 through the afore-described cir-v cuit connections with coils 38 and 39, no current will be induced upon the secondary winding 26a of that stations printer magnet 21a. As a result of the neutralizing efiects of each half of the windings of local transformer coils 25 and 25a two windings 35 and 39 of transformer 65, whereby each neutralizes the magnetic efiect of the other of the two windings resulting in zero impedance. These secondary power current pulsations travel in opposition to each other. over windings 34 and 35, but in the same direction over lines 29 and 32 to the mid-point of local transformer primary winding 25, it being noteworthy that because current flows in the same phase over lines 29 and 32 to the halves of winding 25, no current will be induced upon the transformer secondary winding 23, but the secondary pulsations from coil I5 without appreciable impedance loss will traverse in series the windings 2 3 and 23 of the vibrating printer motor and transmitter element to condenser filtered ground. When the stations I8 and I3 are in communication with each other and while the signaling contacts 28 and 28a remain closed, the current undulations over lines 32, 33, 29 -and-3i are continuous sine wave undulations as portrayed by the curve ilIIi, Fig. 14, no distinction being noted in any of its waves at this time whereby the length of a signal interval is set 011 or defined.

When signaling is initiated as by opening of one of the contact pairs 28 or 28a, depending upon the direction of communication, then corresponding breaks in the line 25 and interruptions in line 3I are effected so that the resulting pattern of the alternating current wave on these lines for the character A is after the manner illustrated in the curve I52, Fig. 14. As a consequence of the intermittent line breaks or interruptions, current surges obtain over the companion conductors 32 and 33 with the result that on these lines the signal pattern is such as is portrayed by the curve I03, increasing the amplitude of both lobes 01' each full wave during those component intervals of each signal in which no current obtains, on the lines 29 and 3|. Since the effect of coils 25 and 25a of inducing a secondary voltage on the windings 25 and 25a, obtains only during the signal intervals of interruption, that is, when the contact pairs 28 or 28a are open, then it follows that print magnets 21 and 21a are energized by an alternating current wave induced from the primaries 25 and 25a during the break intervals as best portrayed by the curve'IM.

Since the secondary winding I5 of the power upon the other half, no magnetic circuit is established on either side of these transformers; moreover, because winding 35 opposes winding 38 and because winding 34 opposes winding 38 there prevails a minimum of impedance in the respective legs of these circuits so long as the described balance is maintained. The opening of one of the circuit legs by reason of the separation ofcontact pair 28, for example, will, however, cause current to be induced upon one of the secondary windings, as will now be described.

With the opening of one of the transmitting contact pairs such as contact pair 28, there is not only removed one of the balancing halves of the coil 25, permitting the other half to actuate magnet 21, but, through effectively removing from the circuit its coil 34 of transformer ii, the winding 38 is permitted to act as an impedance and to reduce the current in circuit 36. The major portion of current from supply line 36 is thereby diverted and flows over the other leg 33 of the parallel paths and through the winding 39. In consequence of this effect, and since the impedance of coil 38 reduces the current flow through the leg 3|, current is increased through leg causing the upper half of transformer winding 25a to induce a voltage upon the secondary winding 26a at station I9. The secondary windings 26 and 26a are illustrated as being directly coning thereby that these elements are operated in response to the induced alternating current. It

is believed well established that where it is deemed advantageous to operate the print magnets by means of direct current, the appropriate rectification of the induced signal may be had by well-known practices whereby the alternating current signal may be converted into a direct current signal simulating conventional simplex communication practice.

In communication held in the reverse direction the opening of contact pair 280. through the operation of the keyboard at station 69 will have a corresponding effect upon the receiving printer magnet 21 at station I8. Thus, there is described a system of telegraph communication in which a central station supplies the operating and signaling current to a plurality of outlying subscribers stations.

A-further modification in which the present invention finds particular application is featured in Fig. ,12 wherein there is illustrated a central station I43 and two respective outlying stations I44 and I45. In this system alternating current originates at a source I45 in the central oflice and is impressed through the primary winding I41 of a power transformer upon a pair of secondary windings I48 and I49 serving stations I44 and I45, respectively.

Each one of the subscriber or outlying stations I44 or I45 is connected with the central office by means of a. pair of conductor lines I5I and I52 or I5Ia and I520, as is noted in Fig. 12. 'Lines I5I and I52 leading to station I44 form part of a loop circuit having the afore-described power transformer secondary winding I48 in series with a pair of additional transformer windings I53 and I54. Each loop circuit also consists of a pri- 2,seo,sso 7 duce a record simultaneously at the two stationsmary windin 52 effectively I56, a primary of cted ov'e'r wire I constituting the h the local station t Thereupon, an cated to the print resultof the opening of con ransformer.

induced voltage is communi- I62. Moreover, as a tact pairs I6 I, it is to I and I45.

In this system as with the one described in connection with FigL'7, a normal signal pattern prevailing over lines I5I and I52 is represented ing current wave undulations become characten In Fig. 13, a print hammer designated I64 is indicated as an integral element of a. biased armature under the control'of an electromagnet I65 ata receiving station I 61. Alternating current is obtained from a common regulated source at both the receiving station I61 andthe transmitting station I66. The vibrating frequency of .results of operation can be'obtained without iden- 5a is without current while tical phase conditions obtaining at all times.

The contact pair I69 which is normally open is periodically closed in accordance with the opera- I the lower winding I56a obtains a preponderant tion of a keyboard apparatus and its performance may be identical with that of contact pair I6I surge from the second current is increased I54a, by induction fro ar I49, As a consequence,

secondary winding mary I54 and since described above. Upon the closure of such con-- tact pair, a circuit I68 is completed for energiznal transmitted over line I 68 is'designated I65 on thechart, Fig. 14, and it is to be noted that the induced alternating current of magnet I65 resembles that of magnets I62 and 21 discussed above.

is to be noted ag ecause no current upon the seconda winding I53 du to the open condi-' The instants at which armature I64 is forced against the type wheel maycorrespond with the first or secondhalf cycles of each double lobed wave; This will depend upon the design characteristics of magnet I65. In other words, for some tion at cont circuit I5Ia of station destroys the balance of t 0 current is available in 'I'his momentarily e circuits I5Ia and l52a signal generation contact pair I6I, vibration freq over but one-half there is caused to control upon the uency which is t of the windings be induced a furth print magnet I62 I55 and I56, er signal line so as to propurposes it may; be preferable to arrange polar magnet I65 so that the first half-wave of a comclaims.

The invention claimed is:

In a printing telegraph apparatus, aztype wheel carrying shaft, a tape advancing shaft, said shafts motor driven by alternating electrical 7 energy received over a line, a type wheel carrying signal composition,

ing fractional sign elements to be integrated dura print hammer, and means responsive to cyclic amplitude variations in said electrical energy for actuating said print hammer under control of said amplitude variations and at variable cyclic intervals during asingle rotation of said type wheel carrying shaft for producing an integrated character.

2. In a printing telegraph system, a type wheel having a plurality of type producing fragments each capable of printing an alphabetical or numerical character portion, means responsive to the undulations of an alternating current wave for advancing the fragments on said type wheel successively before a printing position, and a print hammer responsive to variations in said alternating current wave for eifecting printing engagement during corresponding character fragment presentations.

3. In a printing telegraph apparatus, a type carrying member including a plurality of character printing fragments, each shaped to reproduce a part of an alphabetical or numerical character image, means for presenting said character fragments sequentially in printing position, a print hammer, and electromagnetic means responsive to impulse modulations induced upon an operating power line for actuating said print hammer to selectively engage said character fragments.

4. In a system of printing b character fragment composition, the combination including a type wheel having a plurality of printing fragments distributed peripherally thereon at regular angular intervals, a pulsating motor for operating said type wheel to present its printing fragments in sequence, and a print hammer responsive marginally to superimposed current modulations for bringing a strip of material into engagement with corresponding ones only of said character fragments.

5. In a printing telegraph apparatus, a type carrying member having a plurality of fractional printing elements to be integrated during signal composition, motive power means driven by the undulations of an alternating-current received over the line for driving said type wheel, a percussion printing member, and means nonresponsive to the regular undulations of said alternating current wave, but responsive to cyclic amplitude variations of said current and effective to engage said type wheel in response to said cyclic amplitude variations for producing an integrated character.

6. A printing telegraph apparatus comprising ments sequentially in printing position, a print,

a rotary type wheel having a plurality of periph-- erally disposed character printing fragments.

means to advance said type wheel in accordance with groups of successive undulations of an operating current so as to cause to be presented said type wheel fragments at a printing zone in cyclic phase relationship with said wave undulation l over a line for moving said type carrier in continuous step-by-step movements, and means responsive to predetermined cyclic amplitude variations in said alternating electrical energy for actuating said print hammerat various intervals during each rotary cycle of said type carrier for producing an integrated character.

9. In a printing telegraph system, a type member having a plurality of character image composing fragments for printing alphabetical or numerical characters, means responsive to the undulations of an alternating current wave for advancing the fragments on said type member sequentially through a printing location, and a print hammer responsive to variations in said alternating current wave for effecting printing engagement during corresponding character fragment presentation at said location.

10. Inc. printing telegraph apparatus, a carrying member including a plurality of character composition fragments, each shaped to reproduce a portion of one or more alphabetical or numerical characters, means for presenting said fraghammer, and electromagnetic means responsive to irregularities induced upon an operating power line for actuating said print hammer to selectively engage against corresponding ones of said carrying member, character fragments to effect printed character composition.

11. In a system of printing, the combination including atype wheel having a plurality of fractional character elements distributed peripherall thereon, said elements adapted to be integrated during signal'composition, an alternating current motor for operating said type wheel to present its typing. elements successively to the printing; locus; nd'a print hammer responsive to cyclic'amplitude modulations superimposed upon the normal cyclic undulations of an alternating curl'nflwaflfi for striking against said type wheel correspondingly to produce an integrated char- 'acter.

1 2. A printing telegraph apparatus comprising a cyclically rotatable type wheel having a plurality' of character printing fragments, means to groups, a striker normally nonresponsive to said current undulation, and means responsive to a superimposed undulation of greater amplitude for actuating said striker in accordance with the presentation of corresponding ones only of said printing fragments. I

I. In a printing telegraph mechanism, apparatus for advancing a strip of material in stepby-step movements past aprinting zone, a type carrying wheel having a plurality of type elements each presentable for printing opposite said material during brief rest intervals. and between said successive strip advancing movements, at viadvance said type wheel in accordance with succ'essive undulations of an alternating current so -as to cause to be presented said type wheel fragments sequentially at a printing zone in phase relationship with said wave undulations, a striker, and means responsive to superimposed undulatlons for actuating said striker in accordance with the presentation of corresponding ones only of said printing fragments.

13. In a printing telegraph mechanism, apparatus for advancing a strip in step-by-step-manner, a type carrier having a plurality of type elements, means for printing by striking said strip against said carrier elements during brief rest intervals and between said successive tape advancing movements said means including a print hammer responsive to superimposed current modifications but normally inert to normal alternating current modulations, and a vibrating motor for actuating said type carrier and said strip advancing mechanism.

14. A telegraph printing mechanism, power driven and selectively controlledby an altemating current-sent over a line, comprising a carrier of character printing fragments, a motor responsive to the alternating current for moving said carrier so as to present successively all of its fragments before a printing zone, and a print hammer including means responsive but marginally to electrical variation produced upon the current for striking against said fragments correspondingly.

15. In a system of telegraphic signaling, a telegraph motor element having a period of vibrastation, a second station, means common to said tion coinciding with a predetermined alternating current frequency constant, telegraph receiving I apparatus actuated by said motor element including means responsive to an initial wave modulation and means responsive to ensuing wave modulations, transmitting control means for superimposing initial wave modulations upon said current, and signal forming means responsive to subsequent supervision for superimposing said ensuing modulations upon said current. v

16. In a printing telegraph system, a transmitter station, a receiver station, means for supplying a current of fundamental wave frequency on a transmission circuit connecting said stations, a vibrating element tuned to vibrate at a predetermined frequency corresponding to said fundamental frequenc a set of keys, means under the control 01' any one of said set of keys for ampli fying a wave modulation of said fundamental frequency, and means individual to any key of said set. for affecting a characteristic wave modulation for designating signal cycles.

17. In a system of telegraph signaling, a first wave frequency on a transmission circuit connecting said ions, apparatus at said stations including k yboard transmitting and rotary printing mechanisms having instrumentalities tuned to said fundamental frequency, means under the control of any one of the keys of said keyboard transmitting mechanism for modifying predetermined cycles of said current in accordance wlth'elements of a character corresponding to the key operated, and means associated with said second station responsive to the modified cycles of said frequency current for initiating and controlling printing operations.

18. A method of signaling which includes th steps of transmitting a plurality of alternating current undulations of uniform amplitude constituting a signal, modifying the amplitude of certain ones of the undulations in accordance with fractional sign elements to be integrated during signal composition, and effecting printing operations'u'nder the control of said modified undulations for reproducing an. integrated character by the initiation of a control magnet responsive to said modified undulations only. a

19. In a signaling system, a transmitting station, transmitting apparatus at said station, a receiving station, means to transmit constant altematingcurrent from said transmitting to said receiving stations, an element at said transmitting station responsive by oscillation to said alter- .nating current frequency, a signal transmitting device at said transmitting station actuated by said element, and means for modifying an initial cycle of said alternating current and for coupling said oscillating element to the transmitting apparatus at said transmitting station.

LOUIS M. POTTS. 

